We propose to study the effects of substitution of deuterium oxide and other polar solvents on the properties of sodium and potassium channels in membranes of voltage-clamped Myxicola giant axons and myelinated nerve and on the properties of linear and voltage-dependent channels in artificial bilayer membranes. Properties to be investigated include kinetic and steady-state parameters for the ionic currents, single channel conductance selectivity, asymmetry currents, acid-base properties, and toxin binding. In addition, cell membrane permeability to deuterated cations will be examined.